// coordinateTransform.js

// WGS-84 转 GCJ-02（高德坐标系）转换函数
export function transformGPSToGaode(wgLat, wgLon) {
  const pi = 3.14159265358979324
  const a = 6378245.0 // 地球半径
  const ee = 0.00669342162296594323 // 偏心率

  // 判断是否在中国范围内
  if (outOfChina(wgLat, wgLon)) {
    return [wgLon, wgLat] // 如果不在中国，返回原始坐标
  }

  let dLat = transformLat(wgLon - 105.0, wgLat - 35.0)
  let dLon = transformLon(wgLon - 105.0, wgLat - 35.0)
  const radLat = (wgLat / 180.0) * pi
  let magic = Math.sin(radLat)
  magic = 1 - ee * magic * magic
  const sqrtMagic = Math.sqrt(magic)
  dLat = (dLat * 180.0) / (((a * (1 - ee)) / (magic * sqrtMagic)) * pi)
  dLon = (dLon * 180.0) / ((a / sqrtMagic) * Math.cos(radLat) * pi)
  const mgLat = wgLat + dLat
  const mgLon = wgLon + dLon
  return [mgLon, mgLat]
}

// 纬度转换
function transformLat(x, y) {
  let ret = -100.0 + 2.0 * x + 3.0 * y + 0.2 * y * y + 0.1 * x * y + 0.2 * Math.sqrt(Math.abs(x))
  ret += ((20.0 * Math.sin(6.0 * x * Math.PI) + 20.0 * Math.sin(2.0 * x * Math.PI)) * 2.0) / 3.0
  ret += ((20.0 * Math.sin(y * Math.PI) + 40.0 * Math.sin((y / 3.0) * Math.PI)) * 2.0) / 3.0
  ret += ((160.0 * Math.sin((y / 12.0) * Math.PI) + 320 * Math.sin((y / 30.0) * Math.PI)) * 2.0) / 3.0
  return ret
}

// 经度转换
function transformLon(x, y) {
  let ret = 300.0 + x + 2.0 * y + 0.1 * x * x + 0.1 * x * y + 0.1 * Math.sqrt(Math.abs(x))
  ret += ((20.0 * Math.sin(6.0 * x * Math.PI) + 20.0 * Math.sin(2.0 * x * Math.PI)) * 2.0) / 3.0
  ret += ((20.0 * Math.sin(x * Math.PI) + 40.0 * Math.sin((x / 3.0) * Math.PI)) * 2.0) / 3.0
  ret += ((150.0 * Math.sin((x / 12.0) * Math.PI) + 300.0 * Math.sin((x / 30.0) * Math.PI)) * 2.0) / 3.0
  return ret
}

// 判断是否在中国
function outOfChina(lat, lon) {
  return lon < 72.004 || lon > 137.8347 || lat < 0.8293 || lat > 55.8271
}
